<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
    <title>Title</title>
    <script src="../jquery/jquery-3.2.1.min.js"></script>
    <script src="../js/bootstrap.min.js"></script>
    <link rel="stylesheet" href="../css/bootstrap.css">
</head>
<body>

    <div class="container">

        <h3>下拉菜单</h3>
        <div class="dropdown">

            <button class="btn btn-primary dropdown-toggle" data-toggle="dropdown">下拉菜单<span class="caret"></span></button>

            <ul class="dropdown-menu">
                <li><a href="#">一</a></li>
                <li><a href="#">一</a></li>
                <li><a href="#">一</a></li>
                <li><a href="#">一</a></li>
                <li><a href="#">一</a></li>
            </ul>
        </div>

    </div>
</body>
</html>